Nanofluid Filled Enclosures: Potential Photo-thermal Energy Conversion and Sensible Heat Storage Devices

TL;DR

This paper investigates nanofluid filled enclosures as efficient devices for photo-thermal energy conversion and heat storage, analyzing how nanoparticle volume fraction influences their performance and fundamental limits.

Contribution

It models the optical charging and energy redistribution in nanofluid enclosures, revealing optimal conditions for thermal storage and discharging capacities based on nanoparticle concentration.

Findings

Nanofluid enclosures outperform surface absorption modes in heat storage and discharging.

Lower nanoparticle volume fractions enhance volumetric absorption efficiency.

Volumetric absorption mode yields 7-27% higher storage and 16-47% higher discharging capacities.

Abstract

In the present work we propose "nanofluid filled enclosures" as potential photo-thermal energy conversion and sensible heat storage devices. Herein, the optical charging of the nanofluid has been modeled as "solar radiant energy - nanoparticles" interaction. The subsequent energy redistribution has been modeled as coupled transport phenomena involving mass, momentum and energy transport. In particular, nanofluid filled enclosure with adiabatic, and isothermal (through convective) boundaries have been analyzed to decipher the fundamental limits of sensible heat storage and thermal discharging capacities respectively. Furthermore, the effect of nanoparticles volume fraction on the photo-thermal energy conversion mechanisms and its redistribution thereof has been critically investigated. Detailed analysis reveals that under similar operating conditions, in volumetric absorption mode (i.e., at low nanoparticles volume fraction) nanofluid filled enclosure has higher sensible heat storage (7% - 27% higher) and thermal discharging (16% - 47% higher) capacities than in the corresponding surface absorption mode (i.e., at high nanoparticles volume fraction). Overall, "nanofluid filled enclosures", particularly in volumetric absorption mode, could be deployed for efficient solar thermal conversion and storage.